JP-A-2003-226446 discloses a conventional image forming device. The image forming device comprises a housing, a duct, through which an air in the housing is caused to flow, and a detection element arranged in the duct to detect the presence of a detected body.
More specifically, the image forming device comprises conveyance means that conveys a recording sheet along a conveyance path and discharges the recording sheet outside the housing, and an image forming unit that forms an image on a recording sheet midway on the conveyance path.
The duct is arranged this side of the image forming unit on the conveyance path to comprise an intake duct arranged on one surface side of a recording sheet conveyed along the conveyance path, a guide that abuts against the other surface of the recording sheet conveyed along the conveyance path to guide the recording sheet, and an exhaust duct arranged on the other surface of the recording sheet conveyed along the conveyance path. An air in the housing is sucked through an intake hole into the intake duct to be guided toward the exhaust duct, and an air guided from the intake duct is discharged through an exhaust hole from the exhaust duct.
The detection element is an optical element provided in the intake duct to comprise a light emitting diode that emits light toward the conveyance path and a photoreceptor that receives a reflected light in the case where light emitted from the light emitting diode strikes against a detected body present on the conveyance path. The detection element detects the presence of a recording sheet as an example of a detected body between the intake duct and the exhaust duct, that is, this side of the image forming unit on the conveyance path.
With the conventional image forming device constructed in this manner, when a recording sheet conveyed along the conveyance path passes between the intake duct and the exhaust duct, an air guided to the exhaust duct from the intake duct pushes a recording sheet against the guide. Therefore, an interval between the detection element and a recording sheet is hard to vary. Also, with the image forming device, an air flowing in the intake duct readily removes foreign matters, such as paper powder, etc., adhering to the detection element.
With the image forming device, since the detection element is exposed to an air flowing in the intake duct, it is possible to restrict temperature rise of the detection element, thus enabling surely demonstrating the detecting performance of the detection element. Consequently, it is possible to improve the detection accuracy, with which a detected body is detected.